Trial accounts are not associated with a specific district or licenses. Register your account with your district/school by following these steps: http://join.ccclearningportal.org/.
This document describes how to fill out the registration steps. Note that you will not receive the activation email mentioned after clicking "send activation email" in step 5. Instead you will be able to sign onto the Learning Portal at https://ccclearningportal.org/, where you will then be able to select "Licenses" under your name dropdown and claim the resources you need.
If you encounter trouble logging in after completing the registration steps, contact Tech Support.